1. Field of the Invention
The present invention relates to a printer that holds a recording medium wound in a roll and that prints on the recording medium.
2. Description of the Related Art
For example, among printers that print on a recording medium wound in a roll, are those capable of being used in changeable installation orientations such as “upright” or “horizontal”. Among such printers are those facilitating simplification of recording medium replacement by employing a configuration that does not support axially a core part of the recording medium wound in a roll but supports, from below, the recording medium wound in a roll.
In printers employing a configuration to support the recording medium wound in a roll from below, the position at which the recording medium is stable in the printer differs according to the installation orientation of the printer. Accordingly, a detection point suitable for detecting that the remaining amount of the recording medium is a predetermined amount or less, i.e., a near end, differs according to the installation orientation of the printer.
Conventionally, as a technology to realize near end detection, for example, a printer includes a housing unit that houses a roll of recording paper and includes multiple guiding units each positioning the recording paper at a predetermined position as the diameter of the roll of the recording paper becomes smaller, and a paper end detecting unit that detects that the remaining amount of the recording paper is a predetermined amount or less, by a sensor entering a space of a core part of the recording paper, where the paper end detecting unit is rotatably attached to the accommodating unit such that each sensor corresponds to each of the guiding units (see, e.g., Patent Document 1 below).
Further, as a technology to realize near end detection, for example, a printer includes a printer main body whose installation orientation is changeable in two ways, a printing unit equipped in the printer main body, a roll paper housing unit equipped in the printer main body and having a mounting surface supporting a circumferential surface of the roll paper irrespective of changes in the installation orientation of the printer main body, and a roll paper displacement detecting unit that detects a displacement of a central portion of the roll paper caused by the weight of the roll paper, where the roll paper displacement detecting unit includes a mechanism having a first and a second actuator that can swing about a pivot rotatably fitted to the printer main body, that extend in two different directions from the pivot, and that are displaced according to displacement of a central portion varying in two ways and by the weight of the roll paper, and a sensor whose output signal is switched according to variations in state associated with the rotation of the pivot commonly generated by both of the displacements of the first and the second actuators (see, e.g., Patent Document 2 below).
For example, a printer including a paper holder that accommodates a roll of paper and that includes a guiding unit positioning the paper, whose diameter decreases, at a predetermined accommodation position, and a paper end detecting unit that detects that the remaining amount of the paper is a predetermined amount or less by a sensor contacting an end surface of the paper accommodated in the paper holder, where the printer further includes multiple guiding units corresponding to installation states of the printer, and multiple sensors corresponding to the guiding units. The sensors are disposed in a range formed by a trace of the roll center formed at each step of the diameter reduction of the paper, according to the guiding units, and the inner face of the paper holder connecting the guiding units (see, e.g., Patent Document 3 below).
[Patent Document 1] Japanese Patent Publication No. 3480225
[Patent Document 2] Japanese Patent Publication No. 3785288
[Patent Document 3] Japanese Patent Application Laid-Open Publication No. 2002-234223
In the conventional technique described in Patent Document 1, the paper end detecting unit must be rotated according to the installation orientation each time the installation orientation of the printer is changed. Therefore, a problem arises in that the setting operation concerning the detection of the near end is troublesome.
In the conventional technique described in Patent Document 2, the first and the second actuators are integrated to be one member. Therefore, a problem arises in that the detection precision of each of the actuators cannot be adjusted individually. Further, a problem arises in that the precision in detecting the near end cannot be adjusted for each installation orientation.
In the conventional technique described in Patent Document 3, when the position of the roll paper in the paper holder changes as the paper is consumed, i.e., when the roll paper irregularly moves in the paper holder, detection accuracy is degraded. Therefore, a problem arises in that it is difficult to secure excellent accuracy in detecting the near end.
For example, some users of the printer may determine the amount remaining of a recording medium wound in a roll by visually observing a marking provided at an end portion (the starting portion of the winding) of the recording medium, and may not use the function of near end detection. In this case, the detecting and notification of the near end executed by the printer are rather troublesome and therefore, the function of near end detection may be deactivated.
In the conventional techniques described in Patent Documents 1 to 3, an operation to deactivate the function of near end detection must be executed using control by software to deactivate the function of near end detection. Therefore, a problem arises in that the operation to deactivate the function of near end detection is troublesome.
To solve the problems associated with the above conventional techniques, an object of the present invention is to provide a printer that may easily and assuredly detect that the remaining amount of the recording medium is a predetermined amount or less (a near end), irrespective of the installation orientation of the printer.
To solve the problems associated with the above conventional techniques, another object of the present invention is to provide a printer that improves general versatility.